Loop heat pipe structure

ABSTRACT

A loop heat pipe structure includes an evaporation chamber, a pipe and a condensing unit. The evaporation chamber has an outlet and an inlet and internally defines a receiving space. A wick structure, a compensation chamber and at least one vapor passage are provided in the receiving space, and the vapor passage has an end communicable with the outlet. The pipe has a first and a second end connected to the inlet and the outlet of the evaporation chamber, respectively, and the first end is located closely adjacent to the wick structure. The condensing unit is externally mounted on the pipe between the first and the second end. With the first end of the pipe being located closely adjacent to the wick structure, the working fluid can flow back to the wick structure more efficiently.

FIELD OF THE INVENTION

The present invention relates to a loop heat pipe structure, and moreparticularly, to a loop heat pipe structure that enables upgradedvapor-liquid circulation efficiency in the loop heat pipe.

BACKGROUND OF THE INVENTION

The currently available electronic apparatus all have enhancedperformance. As a result, electronic elements in the electronicapparatus for signal processing and computing also produce more heatthan previous similar electronic elements. The most commonly used heatdissipation elements include heat pipe, heat sink, vapor chamber and soon. These heat dissipation elements are in direct contact with theheat-producing electronic elements to enable further enhanced heatdissipation performance of the electronic elements and prevent the samefrom burning out due to overheat.

Further, fans can be mounted in the electronic apparatus to enableforced heat dissipation to remove heat from the heat dissipationelements. While fans can indeed upgrade the heat dissipation performanceof the electronic apparatus, they are not suitable for use in theelectronic apparatus that have a very limited internal space. Therefore,space is also an important factor to be carefully considered whendesigning the heat dissipation elements.

Based on the concept of vapor-liquid circulation in a heat pipe, a loopheat pipe structure in the form of a loop module has been developed. Theloop heat pipe is formed by combining an evaporation chamber with acondensing unit using a pipe connected to between them. The advantage ofthe loop heat pipe is having its own heat dissipation unit to providebetter evaporation and condensation circulation effect. The evaporationchamber has a wick structure disposed therein for storing theliquid-phase working fluid that flows back into the evaporation chamber.The wick structure is provided with a plurality of grooves, in and alongwhich the vapor-phase working fluid flows. The evaporation chamber hasat least one surface in contact with a heat source to absorb andtransfer heat produced by the heat source to the working fluid stored inthe wick structure, the working fluid in the wick structure is thereforeheated and evaporated. The vapor-phase working fluid flows through thegrooves into the pipe connected to between the evaporation chamber andthe condensing unit to finally spread in the condensing unit. Thevapor-phase working fluid passing through the condensing unit is thencondensed into liquid-phase working fluid again and flows back into theevaporation chamber to complete one cycle of vapor-liquid circulation inthe loop heat pipe.

For the currently available flat-type evaporator used in the loop heatpipe, there are two ways for arranging the compensation chamber and thevapor core (i.e. the wick structure with vapor passages) in theevaporator. In the first way, the compensation chamber and the vaporcore are vertically positioned to overlap with each other. In the secondway, the compensation chamber and the vapor core are positioned at twohorizontally spaced positions.

The flat-type evaporator with overlapped compensation chamber and vaporcore has a large height or thickness, and is therefore not suitable fora compact electronic apparatus that has very limited internal space.

As to the flat-type evaporator with horizontally positioned compensationchamber and vapor core, since there is some distance between the workingfluid in the compensation chamber and the vaporizing surface of thevapor core, there are times the working fluid could not be timelysupplied to the vapor core to result in the problem of dry burning ofthe vapor core.

Therefore, it is desirable to work out a way to overcome thedisadvantages of flat-type evaporator in the conventional loop heatpipes.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide an improved loopheat pipe structure, which overcomes the problem of dry-burning wickstructure occurred in the conventional flat-type evaporator withhorizontally spaced compensation chamber and wick structure.

To achieve the above and other objects, the loop heat pipe structureprovided according to the present invention includes an evaporationchamber, a pipe and a condensing unit.

The evaporation chamber has an outlet and an inlet and internallydefines a receiving space. A wick structure, a compensation chamber andat least one vapor passage are provided in the receiving space, and thevapor passage has an end communicable with the outlet. The pipe has afirst and a second end connected to the inlet and the outlet of theevaporation chamber, respectively, and the first end is located closelyadjacent to the wick structure.

The condensing unit includes a plurality of radiating fins externallymounted on the pipe between the first and the second end.

With the inlet of the evaporation chamber or the first end of the pipebeing located closely adjacent to the wick structure, the condensedworking fluid can flow back to the wick structure more efficiently toavoid the problem of dry-burning wick structure as found in theconventional evaporation chamber caused by late compensation of workingfluid to the wick structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present inventionto achieve the above and other objects can be best understood byreferring to the following detailed description of the preferredembodiments and the accompanying drawings, wherein

FIG. 1 is a partially exploded perspective view of a loop heat pipestructure according to a first embodiment of the present invention;

FIG. 2 is an assembled sectional view of the loop heat pipe structure ofFIG. 1;

FIG. 3 is an assembled sectional view of a loop heat pipe structureaccording to a second embodiment of the present invention; and

FIG. 4 is a sectional view showing the loop heat pipe structureaccording to the present invention in use.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with some preferredembodiments thereof and by referring to the accompanying drawings. Forthe purpose of easy to understand, elements that are the same in thepreferred embodiments are denoted by the same reference numerals.

Please refer to FIGS. 1 and 2, which are partially exploded perspectiveview and assembled sectional view, respectively, of a loop heat pipestructure 1 according to a first embodiment of the present invention. Asshown, the loop heat pipe structure 1 in the first embodiment includesan evaporation chamber 11, a pipe 12 and a condensing unit 13.

The evaporation chamber 11 is a flat-type evaporation chamber having anoutlet 111 and an inlet 112 and internally defines a receiving space113. In the receiving space 113, there are a wick structure 114, acompensation chamber 115 and at least one vapor passage 1141. The vaporpassage 1141 has an end communicable with the outlet 111. According tothe present invention, the inlet 112 and the outlet 111 are notnecessarily located at the same side on the evaporation chamber 11, butcan be located at two opposite sides of the evaporation chamber 11. Thecompensation chamber 115 is defined by between the receiving space 113and the wick structure 114. The evaporation chamber 11 is assembled froman enclosure 11 a and a bottom plate 11 b, which are closed to eachother to define the receiving space 113 between them. The compensationchamber 115 and the wick structure 114 are horizontally positioned inthe receiving space 113 side by side.

The vapor passage 1141 can be selectively provided on a wall surface ofthe evaporation chamber 11 facing toward the wick structure 114, i.e. onan inner surface of the bottom plate 11 b, or be provided on one side ofthe wick structure 114 that faces toward a heat-absorbing side of theevaporation chamber 11 in contact with a heat source 3. In theillustrated first embodiment, the vapor passage 1141 is provided on oneside of the wick structure 114 facing toward the heat-absorbing side ofthe evaporation chamber 11. However, it is understood the vapor passage1141 can be otherwise provided on the inner surface of the bottom plate11 b of the evaporation chamber 11.

The wick structure 114 is disposed in the receiving space 113 of theevaporation chamber 11, such that the compensation chamber 115 isdefined by between the wick structure 114 and the receiving space 113.The inlet 112 and the outlet 111 are located in the vicinity of the wickstructure 114. More specifically, the wick structure 114 is locatedbetween the inlet 112 and the outlet 111, while the inlet 112 is locatedabove the outlet 111. When a working fluid 2 filled in the loop heatpipe structure 1 flows into the evaporation chamber 11 via the inlet112, the working fluid 2 will quickly fall into the wick structure 114due to the gravity, so that the work fluid can flow back to the wickstructure 114 more efficiently. When the wick structure 114 is saturatedwith the working fluid 2, any surplus of the working fluid 2 will flowinto the compensation chamber 115. In other operable embodiments, theoutlet 111 and the inlet 112 can be provided on the evaporation chamber11 at the same height, or the outlet 111 can be located higher than theinlet 112, so long as the inlet 112 can be in direct contact with thewick structure 114.

The evaporation chamber 11 further has a liquid passage 116 providedtherein. The liquid passage 116 has an end communicable with the inlet112, and is located at one side of the wick structure 114. Morespecifically, the liquid passage 116 and the vapor passage 1141 arelocated at an upper and a lower side of the wick structure 114,respectively.

The pipe 12 has a first end 121 and a second end 122, which areconnected to the inlet 112 and the outlet 111 of the evaporation chamber11, respectively. And, the first end 121 is located closely adjacent tothe wick structure 114.

The condensing unit 13 includes a plurality of radiating fins 131, whichare sequentially fixed on and spaced along the pipe 12 to be locatedbetween the first end 121 and the second end 122 of the pipe 12.

The working fluid 2 is filled in the evaporation chamber 11 or the pipe12 and is changeable between a vapor phase and a liquid phase. Thevapor-phase working fluid 21 in the evaporation chamber 11 flows throughthe vapor passage 1141 into the pipe 12 via the outlet 111. When thevapor-phase working fluid 21 spreads in the pipe 12 and flows throughthe section of the pipe 12 having the radiating fins 131 fitted thereon,the vapor-phase working fluid 21 is condensed into the liquid-phaseworking fluid 22. The vapor-phase working fluid 21 and the liquid-phaseworking fluid 22 circulate in the entire loop heat pipe structure 1.

The condensing unit 13 is provided on the pipe 12 between the first end121 and the second end 122, and can include a plurality of radiatingfins or a plurality of cooling pipes.

Please refer to FIG. 3, in which a loop heat pipe structure 1 accordingto a second embodiment of the present invention is shown. The secondembodiment is generally structurally similar to the first embodiment,except that the outlet 111 and the inlet 112 in the second embodimentare provided at two opposite sides of the evaporation chamber 11. Morespecifically, in the second embodiment, the outlet 111 and the inlet 112are located at a left and a right side of the evaporation chamber 11,respectively. Further, in the second embodiment, the first end 121 ofthe pipe 12 is extended into the evaporation chamber 11 via the inlet112 to end at a position above the wick structure 114 and far away fromthe compensation chamber 115. Therefore, in the second embodiment, theliquid-phase working fluid 22 flowing into the evaporation chamber 11 isdirectly guided by the first end 121 of the pipe 12 to the wickstructure 114. When the wick structure 114 is saturated with theliquid-phase working fluid 22, any surplus of the liquid-phase workingfluid 22 will flow into the compensation chamber 115 and be storedtherein. With these arrangements, the liquid-phase working fluid 22 canquickly flow back to the wick structure 114 and the problem ofdry-burning wick structure due to insufficient water content can beimproved.

FIG. 4 shows the loop heat pipe structure 1 of the present invention inuse. As shown, in the loop heat pipe structure 1 of the presentinvention, the evaporation chamber 11 has one side in contact with theheat source 3 and the wick structure 114 is correspondingly provided inthe evaporation chamber 11 on the side in contact with the heat source3. When the evaporation chamber 11 absorbs the heat produced by the heatsource 3, the wick structure 114 in the evaporation chamber 11 is heatedand the liquid-phase working fluid 22 adsorbed to the wick structure 114is also heated and finally evaporated to form the vapor-phase workingfluid 21. Since the vapor passage 1141 has an end directly connected tothe outlet 111 of the evaporation chamber 11, the vapor-phase workingfluid 21 flows through the vapor passage 1141 on the wick structure 114to spread into the pipe 12 via the outlet 111 of the evaporation chamber11 and the second end 122 of the pipe 12. When the vapor-phase workingfluid 21 flowing in the pipe 12 passes the section of the pipe 12 havingthe condensing unit 13 provided thereat, the vapor-phase working fluid21 is condensed into the liquid-phase working fluid 22 again. Then, theliquid-phase working fluid 22 flows back into the evaporation chamber 11via the first end 121 of the pipe 12 and the inlet 112 of theevaporation chamber 11. While the liquid-phase working fluid 22 isguided back to the wick structure 114 due to a capillary action and apressure difference existed during the phase transition of the workingfluid 2, the provision of the inlet 112 above the wick structure 114also enables the liquid-phase working fluid 22 to more quickly fall intothe wick structure 114 due to the gravity to advantageously continue thevapor-liquid circulation in the loop heat pipe structure 1.

Any other type of heat dissipation element (not shown) facilitatingincreased condensing effect can also be externally connected to the pipe12 to enable further improved condensing efficiency.

The present invention changes the position of the outlet 111 and theinlet 112 of the evaporation chamber 11 relative to the wick structure114, such that the liquid-phase working fluid 22 flowing back into theevaporation chamber 11 is first guided to the wick structure 114 insteadof the compensation chamber 115. More specifically, since the wickstructure 114 is located directly below the inlet 112, the liquid-phaseworking fluid 22 flowing back into the evaporation chamber 11 via theinlet 112 will first reach the wick structure 114 to be stored therein.When the wick structure 114 is saturated with the liquid-phase workingfluid 22, only the surplus of the working fluid 22 will flow into thecompensation chamber 115 and be stored therein. With these arrangements,it is able to solve the problem of dry-burning wick structure occurredin the conventional flat-type evaporator, which has horizontally spacedcompensation chamber and wick structure, due to a long distance betweenthe working fluid 2 stored in the compensation chamber and the surfaceof the evaporation chamber in contact with the heat source.

The present invention has been described with some preferred embodimentsthereof and it is understood that many changes and modifications in thedescribed embodiments can be carried out without departing from thescope and the spirit of the invention that is intended to be limitedonly by the appended claims.

What is claimed is:
 1. A loop heat pipe structure, comprising: anevaporation chamber having an outlet and an inlet and internallydefining a receiving space; in the receiving space, there being a wickstructure, a compensation chamber and at least one vapor passage; andthe vapor passage having an end communicable with the outlet; a pipehaving a first end and a second end connected to the inlet and theoutlet, respectively, of the evaporation chamber; and a condensing unitbeing externally mounted on the pipe between the first and the secondend.
 2. The loop heat pipe structure as claimed in claim 1, wherein thevapor passage can be selectively provided on one of the followingpositions: a wall surface of the evaporation chamber facing toward thewick structure, and one side of the wick structure facing toward theevaporation chamber; and the vapor passage having an end communicablewith the outlet.
 3. The loop heat pipe structure as claimed in claim 1,further comprising a working fluid filled in one of the evaporationchamber and the pipe; the working fluid being changeable between avapor-phase working fluid and a liquid-phase working fluid; and thevapor-phase working fluid and the liquid-phase working fluid circulatingin an entire internal space of the loop heat pipe structure.
 4. The loopheat pipe structure as claimed in claim 1, wherein the evaporationchamber is assembled from an enclosure and a bottom plate, which areclosed to each other to define the receiving space between them.
 5. Theloop heat pipe structure as claimed in claim 1, wherein the outlet andthe inlet of the evaporation chamber can be selectively provided on thesame side of the evaporation chamber or on two different sides of theevaporation chamber.
 6. The loop heat pipe structure as claimed in claim1, wherein the outlet and the inlet of the evaporation chamber areprovided on two different sides of the evaporation chamber, and thefirst end of the pipe being extended into the receiving space via theinlet of the evaporation chamber to end at one side of the receivingspace distant from the compensation chamber.
 7. The loop heat pipestructure as claimed in claim 4, wherein the evaporation chamber is incontact with a heat source to absorb heat produced by the heat source,such that the wick structure is heated by the absorbed heat and aliquid-phase working fluid stored in the wick structure is finallyvaporized into a vapor-phase working fluid; the vapor-phase workingfluid flowing through the vapor passage to leave the evaporation chamberand spread into the pipe via the outlet of the evaporation chamber andthe second end of the pipe; the vapor-phase working fluid flowingthrough the pipe and being condensed by the condensing unit into theliquid-phase working fluid again, which flowing back into theevaporation chamber via the first end of the pipe and the inlet of theevaporation chamber; the first end of the pipe being extended into theevaporation chamber to end at a position above the wick structure forguiding the liquid-phase working fluid directly to the wick structure;whereby when the wick structure is saturated with the liquid-phaseworking fluid, any surplus of the liquid-phase working fluid flows tothe compensation chamber to be stored therein.
 8. The loop heat pipestructure as claimed in claim 1, wherein the evaporation chamber is aflat-type evaporation chamber with the compensation chamber and the wickstructure being horizontally located in the receiving space side byside.
 9. The loop heat pipe structure as claimed in claim 1, wherein theevaporation chamber further has a liquid passage provided therein; theliquid passage having an end communicable with the inlet of theevaporation chamber and being located at one side of the wick structure,such that the liquid passage and the vapor passage are located at anupper and a lower side of the wick structure, respectively.
 10. The loopheat pipe structure as claimed in claim 1, wherein the condensing unitis selected from the group consisting of a plurality of radiating finsand a plurality of cooling pipes.